The present invention relates to a polysilazane-based coating solution for the formation of an interlayer insulating layer as well as to a method for the formation of an interlayer insulating layer by using the coating solution. More particularly, the present invention relates to a polysilazane-based coating solution for the formation of an interlayer insulating film which is excellent in respect of the storage stability and coating workability and capable of giving an insulating film having denseness and good surface profile and has little problem in safety due to the use of an organic solvent of low toxicity against human body so as to be useful for the formation of an insulating interlayer film in the manufacture of semiconductor devices, liquid crystal display panels and the like as well as to a method for the formation of an interlayer insulating film by the use of the coating solution.
It is sometimes required in the manufacture of various kinds of electronic devices such as semiconductor devices, liquid crystal display panels and the like to form an interlayer insulating film on the surface of a solid substrate. Various coating solutions have been proposed as suitable for the purpose of forming an interlayer insulating film including those coating solutions containing a polysilazane-based resin having high inorganic nature (see Denshi Zairyo (Electronic Materials), 1994, December issue, pages 50-55 and Japanese Patent Kokai 4-341705, 6-73340, 6-128529 and 6-142600).
As compared with conventional coating solutions for interlayer insulation containing an alkoxysilane as the film-forming ingredient, the above mentioned polysilazane-based coating solutions are advantageous and highlighted in recent years by virtue of the outstandingly low content of organic matters in the film-forming ingredient because, in the formation of an insulating film by the process involving coating of the substrate surface with the solution, drying and baking treatment, the amount of the organic constituents lost from the coating layer by thermal decomposition in the baking treatment is very small so that the denseness of the insulating interlayer film is high so much.
The above mentioned polysilazane-based coating solutions, however, are practically not quite satisfactory due to the defects in respects of their low storage stability and irreproducibility of the quality to give interlayer insulating films having reproducibly high denseness and good surface configuration only with difficulties. In addition, sublimation of the polysilazane may take place in the course of the drying and baking treatment usually undertaken at 100.degree. to 300.degree. C. and the sublimates from the coating layer deposit on the inner walls of the baking oven to cause heavy contamination of the oven. Moreover, sublimation of the polysilazane constituents from the coating layer necessarily leads to shrinkage of and crack formation in the coating film. It is presumable that the above mentioned sublimation of the polysilazane constituents is caused by the low molecular weight fractions of polysilazane contained in the polysilazane-based coating solution.
Further, while the organic solvent used for the preparation of the polysilazane-based coating solutions is mostly xylene in view of the relatively high storage stability of the coating solution prepared therewith, xylene is not without safety problems against human health so that it is eagerly desired to replace xylene with another organic solvent of low toxicity but still capable of giving a polysilazane-based coating solution exhibiting good storage stability and coating workability of the coating solution.